Code
 <%@Page Language = "C#" Debug="true" %> 
<%@ import Namespace="System.Xml" %>
<script language="C#" runat="server"> 
    void Page_Load()
    {
        XmlDocument CurrentXml = new XmlDocument();
        CurrentXml.Load(Server.MapPath("stocks.xml"));
        XmlNode root = CurrentXml.LastChild;

        Random rc = new Random();
        int RandomNumber;
      
        for (int i = 0; i < root.ChildNodes.Count; i++)
        {
            RandomNumber = rc.Next(0, 100);
            XmlNode child = root.ChildNodes[i];
            for (int j = 0; j < child.ChildNodes.Count; j++)
            {
                if (child.ChildNodes[j].Name == "price")
                {
                    decimal value = decimal.Parse(child.ChildNodes[j].InnerXml);
                 
                    Random rp = new Random();
                    decimal RandomPrice = rp.Next(0, (int)value);

                    RandomPrice = RandomPrice / 10;
                    string direction = "";
                    if ((RandomNumber % 2) == 1)
                    {
                         direction = "Down";
                        value = value - RandomPrice;
                    }
                    else
                    {
                         direction = "Up";
                         value = value + RandomPrice;
                    }

                    child.ChildNodes[j].InnerText = value.ToString();
                    child.ChildNodes[j + 1].InnerText = direction;
                }
            }

            
        }
        CurrentXml.Save(Server.MapPath("stocks.xml"));
    }
</script>